Storable liquid cementitious slurries for cementing oil and gas wells

ABSTRACT

In the method of the invention, a storable hydraulically-active cementitious slurry is made and used to cement within subterranean foundations for oil and gas wells. The slurry is made from hydraulically-active, cementitious material suitable for oil field purposes and can be stored until needed. During storage, the slurry remains liquid. The slurry is activated when needed for cementing. After pumping the activated slurry into the wellbore, the set cement has properties acceptable for well cementing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to storable cementitious slurries used foroil and gas well cementing, as well as a method of cementing an oil orgas well using the storable slurry.

2. Description of the Prior Art

Hydraulic cements are cements that set and develop compressive strengthdue to a hydration reaction, not drying. Thus, hydraulic cements can setunder water. This setting property serves a variety of purposes.Hydraulic cements are often used for cementing pipes or casings within awell bore of a subterranean formation for the construction of oil, gasand water wells, as well as other purposes, such as squeeze cementing.In the oil and gas industry, successful cementing of well pipe andcasing during oil and gas well completion requires cement slurrieshaving several important properties. The cement slurry must have apumpable viscosity, fluid loss control, minimized settling of particlesand the ability to set within a practical time.

In a typical completion operation, the cement slurry is pumped down theinside of the pipe or casing and back up the outside of the pipe orcasing through the annular space. This seals the subterranean zones inthe formation and supports the casing. The amount of water used informing the cement slurry depends upon the type of hydraulic cementselected and the job conditions at hand. The amount of water used canvary over a wide range, depending upon such factors as the requiredconsistency of the slurry and upon the strength requirement for aparticular job.

Conventional mixing equipment is relatively complex and expensive. Theequipment must wet dry cement powder, homogenize the mix, measure itsdensity and, if necessary, recirculate it, such that additional solidsor mixwater can be added to achieve the desired density. These variedrequirements dictate the equipment's configuration and complexity.

Bulk equipment is usually pressurized so that solids can be transferredpneumatically at the relatively high rates required. Once at thedrilling site, the pneumatically conveyed cementing solids must becorrectly proportioned and mixed with the water, as well as otheradditives to form a pumpable slurry. The slurry must then be tested forthe appropriate density, with the density adjusted to fall within theappropriate range. If cementing solids are not correctly proportioned,the quality of the cement diminishes.

Because conventional cementing slurries set quickly, they cannot be madein advance of their use. Thus, conventional cementing slurries forcementing well bores cannot be made in advance, such as during thedrilling operation. A delay in the drilling operation delays thecementing job. If personnel and equipment for cementing idly wait onsiteuntil the drilling ends, a delay can increase the cost of the cementingjob. A slurry made in advance and stored until needed would allow thepersonnel and equipment to make the storable slurry, regardless ofwhether drilling had ceased.

One object of the invention is to provide a liquid, storable,cementitious slurry that remains liquid over an extended period of timebut can be activated at the time of use to meet specific jobrequirements.

Another object of the invention is to provide a storable cement slurrythat can be made at a different location from the job site. Thisstorable slurry can then be transported to the job site beforecementing.

Another object of the invention is to provide a storable cement slurrythat can be stored in nonpressurized tanks and easily transferred. Inaddition, the mixing equipment used on the job site need only homogenizethe slurry with any additional water and additives as required en routeto the down hole pumps.

Still another object of the invention is to provide an economical methodof cementing a well bore that enhances the quality control of thecementing job.

Another object of the invention is to provide a liquid, storablecementitious slurry that can be used by adding liquid activators to theliquid slurry and proportioning any additional mix water and additivesto further control the slurry's properties.

Another object of the invention is to provide such a liquid, storablecementitious slurry that can be used in a well cementing operation bysimply metering and controlling liquids rather than by mixing dry bulkproducts with liquids.

Another object of the invention is to continuously formulate a liquid,storable cementitious slurry on one site, transfer the slurry to thesite of application where it is activated and its density adjusted, thenpumped into the subterranean formation for cementing.

Another object of the invention is to enhance wellsite efficiency byreducing the time required for the cementing operation. Currentpractices face rate limitations due to the inherent problems of bulksupply, particle wetting and dispersion, etc. Use of a pre-mixed,storable slurry removes these restrictions, permitting the operation tobe carried out consistently at high rates.

SUMMARY OF THE INVENTION

The storable, hydraulically-active, cementitious slurry of the inventionis suitable for cementing within subterranean formations for oil or gaswells. The storable slurry comprises a hydraulically-active cementitiousmaterial of a type suitable for cementing within subterranean formationsfor oil or gas wells; an effective amount of a set retarder to allow thestorage of the slurry with a minimal change of the slurry's setcharacteristics after activation and to allow the reversal of theretardation after adding an effective amount of an activator to theslurry prior to cementing; a suspending agent for maintaining the slurrywith minimal separation of the cementitious material, an effectiveamount of water to form a pumpable slurry and optionally, a dispersantto maintain the fluidity of the mix.

In one method of the invention, a subterranean formation for an oil orgas well is cemented with the storable, hydraulically-active,cementitious slurry formulated by mixing together a hydraulically-activecementitious material, a set retarder, a suspending agent, water, andoptionally a dispersant, wherein the storable slurry's characteristicsminimally change during storage. The storable slurry is stored untilrequired for cementing, at which time it is activated by mixing togetheran activator and the storable slurry, pumped into the subterraneanformation and allowed to set.

In another method of the invention, the density of the slurry ismeasured and adjusted to the desired density for a particular cementingapplication by metering and controlling liquids rather than by mixingdry bulk products and liquids.

In still another method of the invention the steps of the method areperformed at two different locations. In this method, the stable,hydraulically-active, cementitious slurry is formulated at one location,transferred to a second location, activated at the second location, thenpumped into the subterranean formation for cementing.

Additional effects, features and advantages will be apparent in thewritten description that follows.

DETAILED DESCRIPTION OF THE INVENTION

A storable, hydraulically-active, cementitious slurry of the inventionis made from a hydraulically-active cementitious material.Hydraulically-active cementitious materials include materials withhydraulic properties, such as hydraulic cement, slag and blends ofhydraulic cement and slag (slagment) which are well known in the art.The term "hydraulic cement" refers to any inorganic cement that hardensor sets due to hydration. In this disclosure, the term"hydraulically-active" refers to properties of a cementitious materialthat allow the material to set in a manner like hydraulic cement, eitherwith or without additional activation. Hydraulically-active cementitiousmaterials may also have minor amounts of extenders such as bentonite,gilsonite, and cementitious materials used either without anyappreciable sand or aggregate material or admixed with a granularfilling material such as sand, ground limestone, the like. Strengthenhancers such as silica powder or silica flour can be employed as well.Hydraulic cements, for instance, include portland cements, aluminouscements, pozzolan cements, fly ash cements, and the like. Thus, forexample, any of the oilwell type cements of the class "A-H" and "J" aslisted in the API Spec 10, (1st ed., 1982), are suitable hydrauliccements.

The type of slag used for the invention has hydraulic properties. Theslag is preferably ground-granulated blast furnace slag with a minimumglass count of about 95% and a fine particle size of about 1 to about100 μm, preferably less than about 45 μm, most preferably less than 10μm or a fineness of about 310 to about 540 m² /kg. See, e.g., U.S. Pat.Nos. 5,125,455 and 5,106,423. A slag slurry develops little strengthwithout increasing the alkalinity of the slurry to initiate hydration.Slag alone can also produce a brittle set product and fluid loss fromthe slag slurry can be difficult to control.

Slagments are preferably blends of slag and portland cement. Examples ofsuitable slagments include blends ranging from about 90% cement with 10%slag to 10% cement with 90% slag, with a particularly preferred blend of60% slag with 40% cement with all percentages based on the dry weight ofeach component.

Slagment and hydraulic cement are preferred cementitious materials.However, both of these materials react quickly with water and set atroom temperature unless modified, and they are, therefore, much moredifficult to control. The interstitial water of both cement and slagmentslurries is also very aggressive, for example, having a high pH. Yet,storable slurries formed from hydraulic cement, especially portlandcement, or slagment have the best overall performance characteristicsfor well cementing applications.

A set retarder is necessary to prevent the setting of the slurry duringstorage. The characteristics of these set retarders are diverse andimportant. An effective amount of set retarder allows the storage of theslurries with minimal changes in the characteristics of both the storedand activated slurry. It is equally important that this effect isreversible after adding an effective amount or low concentration ofactivator to the slurry, even at low well circulating temperatures. Inaddition, the set retarder should preferably provide some dispersion ofthe slurry without overdispersion, and little effect on the compressivestrength after activation and setting.

Suitable set retarders include glucoheptonates, such as sodiumglucoheptonate, calcium glucoheptonate and magnesium glucoheptonate;lignin sulfonates, such as sodium lignosulfonate and calcium sodiumlignosulfonate; gluconates, such as sodium gluconate, calcium gluconateand calcium sodium gluconate; phosphonates, such as the sodium salt ofEDTA phosphonic acid; sugars, such as sucrose; hydroxycarboxylic acids,such as citric acid; and the like, as well as their blends. Calciumgluconate for hydraulic cement and slagment slurries and sodiumglucoheptonate for slag slurries are especially preferred.

The amount of set retarder can vary, depending on the type ofcementitious material, the type of set retarder selected and the desiredstorage time. Since this disclosure refers to both slags and hydrauliccements, the term "BWOC" refers to by weight of the cementitiousmaterial. For slagments and hydraulic cements, typical amounts ofgluconates and glucoheptonates range from about 0.1% to about 5% BWOC,preferably from about 0.2% to about 1% BWOC, with about 0.5% BWOC ofcalcium gluconate especially preferred. For slags, typical amounts ofgluconates and glucoheptonates range from 0% to about 3% BWOC, withabout 0.1% to about 0.4% BWOC of sodium glucoheptonate especiallypreferred.

Because the cementitious material may separate during storage due toreduced interparticle interactions when compared with normal cementslurries, adding a suspending agent maintains the slurry with minimalseparation of the cementitious material. Certain types of suspendingagents of the type used in the drilling mud industry can be used for thepurposes of the present invention. These suspending agents includepolymers, clays, emulsions, transition metal oxides and hydroxides, andthe like. Because more than one suspending agent can be used in thestorable slurry, in this disclosure, the term "suspending agent" refersto one or more suspending agents. While some particle separation canstill occur over time, routine agitation redisperses the separatedparticles and rehomogenizes the slurry during storage.

However, the long term suspension of storable cementitious slurries canbe somewhat problematic. Both hydraulic cement and slagment slurriespose more difficulties due to the aggressive nature of the interstitialwater. This aggressive nature of the interstitial water hydrolyzes somepolymers, initiates gelation or crosslinking of other polymers andimpairs the long-term support properties of clays by ion-exchange, forexample. Suitable suspending agents for hydraulic cements and slagments,therefore, should not gel, crosslink or hydrolyze polymers, nor impairthe long-term support of clays. Specific examples of suspending agentsuseful for the purposes of the present invention includepolysaccharides, such as welan gums ("BIOZAN", Kelco, San Diego,Calif.), xanthan gums, cellulose and its derivatives like carboxymethylcellulose, polyanionic cellulose ("DRISPAC", Drilling Specialties,Bartlesville, Okla.), carboxymethylhydroxyethyl cellulose, guar and itsderivatives, starch, succinoglycan ("SHELLFLO-S", Shell InternationalChemical Co., Ltd., London, England); polyethylene oxide ("POLYOX PEO",Union Carbide, Danbury, Conn.); clays such as bentonite and attapulgite;mixed metal hydroxides ("POLYVIS", SKW, Trostberg, Germany); as well astheir combinations, and oil-in-water emulsions created with paraffinoils and stabilized with ethoxylated surfactants. "SHELLFLO-S",polyethylene oxide and bentonite are especially preferred for portlandcements and slagments. Slag slurries are preferably suspended usingxanthan gums with or without bentonite clay.

The amount of suspending agent used in the storable slurry depends onthe type of hydraulically-active cementitious material and selectedsuspending agent. For slag, the amount of xanthan gum preferably rangesfrom 0 to about 2 ppb with the bentonite ranging from 0 to about 8 ppb,with about 0.66 of xanthan gum and 0 to about 3 ppb of bentoniteespecially preferred. For hydraulic cement and slagment, the amount of"SHELLFLO-S" preferably ranges from 0 to about 0.4 gpb based on theamount of the mixwater, with about 0.1 gpb to about 0.2 gpb preferred,and bentonite ranges from 0 to about 10 ppb, with 0 to about 3 ppbpreferred. If polyethylene oxide is used alone, the amount preferablyranges from 0 to about 5 ppb with about 0.5 ppb to about 2 ppbespecially preferred. Polyethylene oxide may be combined with any of theother suspending agents.

An optional dispersing agent may be used in the storable slurry tocontrol the fluidity of the slurry. The amount of dispersing agentdepends of the type of hydraulically-active cementitious material used,selected suspending agent and desired density of the storable slurry.Specific examples of dispersing agents include melamine sulfonic acidpolymer condensation product ("SP5", "CORMIX", Warrington, England),sodium polyacrylate ("BEVALOID 6770", Rhone-Poulenc, Watford, England),naphthalene sulfonic acid polymer ("LOMARD", Diamond Shamrock ChemicalsCo., Morristown, N.J.), and sulfonated-styrene maleic anhydride polymer("SSMA"), (Miltemp, Milpark, Houston, Tex.). The preferred dispersingagent is "SSMA" and the amount preferably ranges from 0 to about 5pounds per barrel of mix water, with about 1 to about 3 pounds perbarrel especially preferred.

Mixing water containing the above-mentioned additives with the dryhydraulically-active cementitious materials produces the storableslurry. A sufficient amount of water, preferably fresh water, should beadded to the hydraulically-active cementitious material to form a liquidstorable slurry of suitable consistency. A storable slurry with portlandcement should have a density measuring in the range from about 11 to17.5 lbm/gal and preferably in the range of about 14 to 17.5 lbm/gal,more preferably about 15-16.5 lbm/gal. Storable portland cement slurriesat densities about 17.5 lbm/gal and greater have a tendency to gel orundergo a type of "pack-setting" when stored for prolonged periods.Slurry densities for slag slurries of about 15 lbm/gal are preferable.

Depending upon the particular storable slurry, the amount of mixingwater in the slurry of the present invention ranges from about 30 to 150weight percent based upon the dry weight of cement and preferably is inthe range of about 35 to 90 weight percent.

Under normal conditions, the storable slurries of the invention haveconsiderable longevity. The storable slurry of the invention shouldremain stable as a liquid, preferably for about a week and morepreferably about two to three months without setting. In some cases,storage times in excess of six months will be achieved. Changes inthickening time of the activated hydraulic cement slurries, even afterprolonged storage of the nonactivated slurry, are not excessive and suchchanges are readily determined using techniques known in the art.

At the time of cementing, the stored slurry is activated, pumped intothe well and allowed to set. Activation occurs by adding an activator.The activator initiates hydration and allows the slurry to set after apredetermined pumping time.

The activator must counteract the set retarder while having a minimaleffect on final slurry properties or set characteristics, such asrheology and fluid loss when used in an effective amount. In addition,the activator should be easy to pump and handle, such as a liquid;economical; widely available at reasonable purity; safe to ship andhandle and environmentally acceptable.

Activators for a storable slurry include solutions of Group IA and IIAhydroxides, such as sodium hydroxide, magnesium hydroxide and calciumhydroxide; sulfates, such as sodium sulfate; aluminates, such as sodiumaluminate and potassium aluminate; carbonates, such as sodium carbonateand silicates. Preferred activators are sodium silicates. Sodiumsilicate has a large number of industrial uses which include drillingfluids and waterproofing mortars and cements. For slag slurries a sodiumsilicate ("Crystal 120H", Crosfield, Warrington, England)) with aparticular silica/soda ratio is especially preferred. Sodium silicate("Crystal 100S", Crosfield) with a different silica/soda ratio isespecially preferred for hydraulic cement and slagment slurries. Typicalconcentrations of activator range from about 0 to about 8 gpb of slurry,preferably about 1 to about 3 gpb of slurry and are preferably addedwith additional mixwater.

There are two approaches for controlling the thickening time of theactivated storable slurries. The first approach is to accurately meteror measure out the activator based on a dose-response curve so thestored slurry becomes "less retarded" and provides the desiredthickening time. Because the slope of the dose-response curve may besteep, the slurries may be too sensitive to permit the accurate controlof thickening at the wellsite.

The second approach is to "over-activate" the slurry and add additionalor secondary set retarders, such as lignin sulfonates, tartrates,gluconates, glucoheptonates, and the like, to achieve the desiredthickening time. The "over-activated" slurries respond normally toconventional levels of retarder and exhibit far less sensitivity. Inaddition, "over-activation" might boost the early compressive strengthof the set slurries. A typical concentration of additional set retardersodium lignosulfonate ("R12-1", 40% active, Boregard, Sarpsborg, Norway)ranges from 0 to about 1 gpb.

Extra water is preferably added to the storable slurry duringactivation. This extra water may be fresh water, sea water or brine. Theextra water may contain activator and additional additives, forinstance, potassium chloride, dispersants, viscosifiers, secondaryretarders, liquid supensions of weighting agents and chemical extendingagents.

The activated slurry can be adjusted to the desired density for aparticular cementing application. The slurry density can be increased bythe addition of a liquid suspension of a weighting agent, such astrimanganese tetraoxide. Lower density slurries can be prepared byadding more water and modifying activator concentrations, if required.Thus, storable slurry "concentrates" can be made in advance and dilutedwhen activated. For example, a 12.5 lbm/gal portland cement slurry canbe prepared by adding 2-3 gallons sodium silicate activator per bbl ofslurry and around 38 gallons of additional water per bbl to a storableslurry having the initial density around 15.8 to 16.5 lbm/gal.

Preferably, a pumpable slurry is formed with a measured density rangingfrom about 11 to about 20 lbm/gal, more preferably in the range of about14 to about 16 lbm/gal and most preferably about 15 lbm/gal. Althoughthe latter is a lower density than conventional "neat cement", themechanical properties of the set cement are appropriate for wellcementing applications. Furthermore, the volume yield increases and therheology improves by this slight density reduction.

Once set, the storable slurries of the invention have normal levels ofcompressive strength.

In the preferred method of the invention, a storable cementitious slurryis made using an oilwell type portland cement, for example, "DyckerhoffClass G" (Dyckerhoff Zementwerke, Wiesbaden, Germany). The cement ismixed together with a calcium gluconate (0.5-0.75% BWOC) set retarder, 3ppb of bentonite and about 0.1 gpb "SHELLFLO-S" suspending agent (oralternatively with 2 ppb "POLYOX PEO" alone) and sufficient water toreach a density of about 15.8 to 16.5 lbm/gal. Dispersants, such aspolyacrylate, sulfonated styrene maleic anhydride, naphthalene sulfonicacid polymer, and the like, are well known in the art and can be addedto the above mixture as needed. The resultant slurry can be kept withoccasional agitation for periods of time exceeding twelve weeks undernormal storage conditions.

The storable slurry is activated by adding the necessary amount ofactivator, in this case sodium silicate (100S) is preferably added in anamount of 1 to 3 gpb of slurry before pumping into the well bore. Theactivator is preferably added with a small volume of additional water toadjust the final density of the activated slurry to 15 lbm/gal.

Table 4 shows rheological properties for three storable slurries anddemonstrates that the rheological properties are changed minimally whenkept for prolonged periods. The slurries have some viscosification uponactivation. If such viscosification is undesirable, it can besubstantially eliminated by adding dispersants to the slurry. Table 5shows the rheological properties for three activated slurries anddemonstrates that the rheological properties are minimally changed.

Fluid loss control is essential for many conventional cementingapplications, for example, squeeze cementing and the cementing of linersand production strings. The addition of conventional cementingfluid-loss additives, such as polyvinyl alcohol, styrene-butadienelatex, co- and ter-polymers of acrylamidomethylpropanesulfonic acid,hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose,carboxymethyl cellulose and starch, to storable hydraulic cement andslagment slurries, at the time of activation, provides acceptable levelsof control.

A number of additional factors may affect the performance of thestorable slurries of the invention. Conventional cement slurries, undercertain circumstances, are sensitive to shear and exhibit changes inrheology and thickening time, for example, that depend on the mixingenergy or pipe shear to which they are exposed. The storable slurries ofthe invention do not exhibit undue shear sensitivity and, therefore,should be mixable with a variety of field equipment.

The storable slurry of the invention offers the option of addingmaterial either to the slurry itself or to extra mixwater used to dilutethe slurry to the final design density. It is well known that theresponse of cements to certain additives, for example, dispersants,retarders and gelling agents depends on how the additives are introducedto the slurry. Dry blended additives often elicit qualitativelydifferent performance characteristics than those added to mixwater. Evengreater differences are sometimes seen if additives are added to analready-mixed slurry. The order of addition of activator and additionaladditives to the slurry has little effect on the rheology of theactivated slurry when mixed at normal API shear rates.

The following example is provided to increase the understanding of theinvention, without limiting the scope of the invention.

EXAMPLE 1

All of the experiments using slag were run with slag having a finenessof 420 m² /kg. All experiments with portland cement used "DyckerhoffClass G" or "Cemoil Class G" cement. Slagments were 70/30 blendsordinary portland cement (Castle Cement, Coatbridge, Strathclyde,Scotland) and 420 m² kg fineness slag.

The experimental protocols followed standard laboratory testingprocedures outlined in the API Specification 10. Where necessary, theseprocedures were modified, such as when the order of addition and mixingenergy variables were being studied.

Mixwater was placed in a plastic beaker and stirred with a paddle mixerwhile adding the suspending agent until the suspending agent wasdispersed or hydrated. Next, the set retarder was added while stirringuntil dissolved. Finally the optional dispersant was added whilestirring until dissolved.

The mixwater prepared above was transferred to a Waring blender fittedwith an electronic speed control with the speed adjusted until forming agood vortex. While maintaining the vortex by controlling the blenderspeed, the hydraulically-active cementitious material was added and thetime of addition recorded. After 60 s of stirring the slurry, theblender was stopped.

The slurry was transferred to a Fann 35 viscometer cup while noting theslurry's physical characteristics. The initial slurry rheology wasmeasured, and optionally at 10 s and 10 min., using standard rotor 1,spring 1 and bob 1 viscometer configuration at room temperature.

Next, the slurry was transferred to a wide-mouthed plastic bottle fittedwith a screw top lid and tightly sealed. The bottle was stored forextended periods of time.

At regular intervals during storage, the slurry's condition was checked.Using a small spatula, free water, gel strengths, the separation ofcementitious material particulates, gelation, setting and the generalappearance of the slurry were noted. Then, the slurry was remixedthoroughly by stirring and shaking. When desired, the rheology waschecked as described above. The storage and testing continued until theslurry set hard. The hard set was usually preceded by a period of highslurry viscosity and gelation, rendering the material unusable before itactually set.

The activation and testing of the final slurry was done with eitherfreshly prepared slurry or stored slurry. A similar mixing energy asdescribed in API Spec 10, §5 for conventional cements was used. Theslurry was placed in an electronically controlled Waring blender andstirred at 4,000 rpm for 60 s. The activator plus dilution water and anyadditional additives were then introduced at 4,000 rpm within a 15 sinterval. The mixture was next blended at 12,000 rpm for 35 s.

After final activation and blending, the slurry was tested like aconventional cement slurry. Conventional antifoams could be used toreduce air entrainment as required.

                                      TABLE 1                                     __________________________________________________________________________    STORABLE SLURRY STABILITY TESTING                                                            SUSPENDING AND                                                    SLURRY                                                                              CEMENT                                                                              DISPERSING RETARDER                                                                             TIME                                         No.                                                                              DENSITY                                                                             TYPE  AGENTS.sup.1                                                                             % BWOC WEEKS                                                                              COMMENTS                                __________________________________________________________________________     1 15    Slag  0.33 ppb welan                                                                           0.1    1    stable                                                 gum.sup.2  NaGH.sup.3                                           2 15    Slag  0.9 ppb    0.1 NaGH                                                                             4    stable                                                 xanthan.sup.4                                                                                   7    acceptable/                                                                   settling                                 3 15    Slag  0.66 ppb   0.1 NaGH                                                                             7    stable                                                 xanthan                                                                                         14   acceptable/                                                                   settling                                 4 16    Slag  0.9 ppb xanthan                                                                          0.1 NaGH                                                                             2    mod. gel                                 5 15    Slagment                                                                            0.9 ppb xanthan                                                                          0.5 NaGH                                                                             1    sedimented                               6 15    Slagment                                                                            0.2 gpb SS.sup.5                                                                         0.5 NaGH                                                                             1    stable,                                                                       fluid                                                                    7    stable                                   7 15.8  Portland                                                                            0.7 ppb xanthan                                                                          0.5 NaGH                                                                             1    stable                                                                   2    settling                                 8 15.8  Portland                                                                            0.9 ppb xanthan                                                                          0.5 NaGH                                                                             1    settling                                               +                                                                             1 gpb NSAP.sup.6                                                9 15.8  Portland                                                                            0.7 ppb welan                                                                            0.5 NaGH                                                                             1    stable/gel                                             gum                                                                                             3    gel/thick                               10 15.8  Portland                                                                            0.5 ppb welan                                                                            0.5 NaGH                                                                             2    settling                                               gum                                                            11 15.8  Portland                                                                            0.3 ppb welan                                                                            0.5 NaGH                                                                             1    settling                                               gum                                                            12 15.8  Portland                                                                            1 ppb CMC.sup.7 +                                                                        0.5 NaGH                                                                             1    bad gel                                                0.8 gpb NSAP                                                   13 15.8  Portland                                                                            0.4 ppb CMC +                                                                            0.5 NaGH                                                                             7    stable                                                 0.1 gpb PA.sup.8                                                                                9    set                                     14 15.8  Portland                                                                            1 ppb PAC.sup.9                                                                          0.5 NaGH                                                                             1    bad gel                                 15 15.8  Portland                                                                            1 ppb CMHEC.sup.10                                                                       0.5 NaGH                                                                             1    thixotropic                                                                   gel                                     16 15.8  Portland                                                                            1 ppb Starch                                                                             0.5 NaGH                                                                             1    bad gel                                 17 15.8  Portland                                                                            5 ppb      0.5 NaGH                                                                             1    settling                                               Attapulgite                                                    18 15.8  Portland                                                                            5 ppb      0.5 NaGH                                                                             1    bad gel                                                Attpulgite                                                                    + 0.4 ppb                                                                     xanthan                                                        19 15.8  Portland                                                                            5 ppb BC.sup.11                                                                          0.5 NaGH                                                                             1    thick                                   20 15.8  Portland                                                                            3 ppb BC   0.5 NaGH                                                                             4    stable                                                                   5    some settling                           21 15.8  Portland                                                                            3 ppb BC + 0.5 NaGH                                                                             1    stable                                                 0.03 gpb ppb                                                                  ALCH.sup.12                                                                                     2    bad gel                                 22 15.8  Portland                                                                            2 ppb BC + 8.3                                                                           0.5 NaGH                                                                             1    stable                                                 ppb                                                                           microsilica.sup.13                                                                              2    bad gel                                 23 17    Portland                                                                            5 ppb BC + 0.5 NaGH                                                                             1    sediment                                               0.8 gpb NSAP                                                   24 15.8  Portland                                                                            5 ppb BC + 0.5 NaGH                                                                             2    stable                                                 0.2 xanthan                                                                                     4    mod gel                                                                  5    set                                     25 16.5  Portland                                                                            3 ppb BC + 0.2                                                                           0.5 NaGH                                                                             3    stable                                                 xanthan                                                                                         4    thick                                                                    5    set                                     26 16.5  Portland                                                                            0.2 ppb welan                                                                            0.5 NaGH                                                                             1    bad gel                                                gum                                                            27 16.5  Portland                                                                            0.1% PVP.sup.14                                                                          0.5 NaGH                                                                             1    gel/sediment                            28 15.8  Portland                                                                            oil emulsion.sup.15                                                                      0.5 NaGH                                                                             1    compact                                 29 16.5  Portland                                                                            0.2 gpb SS 0.5 NaGH                                                                             1    settling                                                                 3    compact                                 30 16.5  Portland                                                                            20 ppt XL- 0.5 NaGH                                                                             1    gelled                                                 guar.sup.16                                                    31 16.5  Portland                                                                            5% BWOC Fe.sub.2 O.sub.3,                                                                0.5 NaGH                                                                             1    stable                                                 orange.sup.17                                                                                   3    thick/compact                           32 16.5  Portland                                                                            3% BWOC    0.5 NaGH                                                                             1    gelled                                                 Magneplus.sup.18                                               33 16.5  Portland                                                                            0.2 ppb welan                                                                            0.5    2    stable                                                 gum        CaG.sup.19                                                                           3    compacted                               34 15.8  Portland                                                                            4 ppb BC   0.5 CaG                                                                              3    stable                                                                   4    stable >                                                                      T. Time                                                                       test                                    35 15.8  Portland                                                                            0.27 gpb SS +                                                                            0.5 CaG                                                                              1    slightly                                               0.27 gpb PA            gelled                                                                   7    slightly                                                                      sedimented                              36 15.8  Portland                                                                            0.7 ppb    0.5 CaG                                                                              4    settled                                                xanthan +                                                                     0.32 gpb PA                                                    37 16.5  Portland                                                                            0.2 gpb SS +                                                                             0.5 CaG                                                                              5    stable                                                 0.4 PA                                                                                          6    gel                                                                      7    thick                                   38 15.8  Portland                                                                            3 ppb BC + 0.1                                                                           0.5 CaG                                                                              3    stable                                                 gpb SS                                                                        + 0.3 gpb PA                                                                                    4    bad gel                                 39 15.8  Portland                                                                            3 ppb BC   0.5 CaG                                                                              7    stable                                  40 15.8  Portland                                                                            2 ppb PEO.sup.20                                                                         0.5 CaG                                                                              7    stable                                  41 16.5  Portland                                                                            1.6 ppb PEO                                                                              0.5 CaG                                                                              6    stable                                                 0.5 ppb SSMA.sup.21                                            42 15.8  Portland                                                                            1.5 ppb PEO                                                                              0.5 CaG                                                                              8    stable                                                 1.5 ppb SSMA                                                   __________________________________________________________________________     .sup.1 All concentrations of suspending and dispersing agents are based o     the quantity of mix water.                                                    .sup.2 Welan gum biopolymer, "BIOZAN                                          .sup.3 Sodium glucoheptonate                                                  .sup.4 Xanthan gum                                                            .sup.5 Succinoglycan, "SHELLFLOS                                              .sup.6 Naphthalene sulfonic acid polymer                                      .sup.7 Carboxymethyl cellulose                                                .sup.8 Sodium polyacrylate                                                    .sup.9 Polyanionic cellulose, "DRISPAC                                        .sup.10 Carboxymethylhydroxyethyl cellulose                                   .sup.11 Bentonite clay                                                        .sup.12 Aluminum chlorohydroxide                                              .sup.13 Microsilica, Elkem Chemical, Kristiansand, Norway                     .sup.14 Polyvinylpyrrolidone                                                  .sup.15 5% bvol Lotox oil/95% bvol fresh water stabilized with sulfonated     nonyl phenol ethoxylate surfactant                                            .sup.16 Crosslinked guar                                                      .sup.17 Ferric oxide, fine (±0.5 micron) pigment grade, Bayer AG,          Germany                                                                       .sup.18 Magnesia cement                                                       .sup.19 Calcium gluconate                                                     .sup.20 Polyethylene oxide, "POLYOX                                           .sup.21 Sulfonated styrene maleic anhydride                              

                                      TABLE 2                                     __________________________________________________________________________    STORABLE SLURRY SET RETARDATION                                                                         STORAGE TIME (DAYS)                                              CONC.        CEMENT TYPE.sup.1                                   SLURRY       %    SUSPENDING   SLAG-                                                                             PORT-                                      DENSITY                                                                             RETARDER                                                                             BWOC AGENT   SLAG MENT                                                                              LAND                                       __________________________________________________________________________    15    NaGH.sup.2                                                                           0    0.66 ppb                                                                                8                                                                   xanthan.sup.3                                               15    NaGH   0.1  0.66 ppb                                                                              103<                                                                  xanthan                                                     15    NaGH   0.2  0.66 ppb                                                                              103<                                                                  xanthan                                                     15    NaGH   0.4  0.66 ppb                                                                              103<                                                                  xanthan                                                     15    NaGH   0.3  2 ppb BC.sup.4                                                                              13                                            15    CaG.sup.5                                                                            0.5  0.12 gpb     54<                                                              SS.sup.6                                                    15.8  NaGH   0.2  0.45% BWOC        9                                                           xanthan                                                     15.8  NaGH   0.3  0.45% BWOC       24                                                           xanthan                                                     15.8  NaGH   0.5  0.45% BWOC       39                                                           xanthan                                                     16.5  NaGH   0.7  0.45% BWOC       38                                                           xanthan                                                     16.5  NaG.sup. 7                                                                           0.5  3 ppb BC         58<                                        16.5  CaG    0.2  3 ppb BC         17                                         16.5  CaG    0.4  3 ppb BC         38<                                        16.5  CaG    0.5  3 ppb BC         61<                                        15.8  CaG    0.7  3 ppb BC         54<                                        16.5  Citric 0.5  3 ppb BC         22                                               acid                                                                    16.5  CSLS.sup.8                                                                           0.5  3 ppb BC          8                                         16.5  Sucrose                                                                              0.5  3 ppb BC         Gel                                        15.8  CaG    0.5  1.5 ppb          60<                                                          PEO.sup.9                                                   15.8  CaG    0.5  1.5 ppb          60<                                                          PEO                                                                           1.5 ppb                                                                       SSMA.sup.10                                                 __________________________________________________________________________     .sup.1 Time in days indicates when the stored slurry hardened. In some        cases the slurry would be unsuitable for use prior to this time.              .sup.2 Sodium glucoheptonate                                                  .sup.3 Xanthan gum                                                            .sup.4 Bentonite clay                                                         .sup.5 Calcium gluconate                                                      .sup.6 "SHELLFLOS                                                             .sup.7 Sodium gluconate                                                       .sup.8 Calcium sodium lignosulfonate                                          .sup.9 Polyethylene oxide                                                     .sup.10 Sulfonated styrene maleic anhydride                              

                                      TABLE 3                                     __________________________________________________________________________    ACTIVATION OF STORABLE SLURRIES                                               SLURRY       CEMENT                                                                              ACTIVATOR COMMENTS                                         DENSITY                                                                             RETARDER                                                                             TYPE  TYPE  CONC                                                                              21° C. (70° F.)                    __________________________________________________________________________    15    0.1%   Slag.sup.2                                                                          Na sulfate                                                                          10 ppb                                                                            Ineffective                                            NaGH.sup.1                                                              15    0.1% NaGH                                                                            Slag  Soda ash                                                                            10 ppb                                                                            49 hrs set                                       15    0.1% NaGH                                                                            Slag  Sodium                                                                              2 gpb                                                                             14 hrs set,                                                         silicate  suitable                                                            100S      activator                                        15    0.1% NaGH                                                                            Slag  30% NaOH                                                                            0.5 gpb                                                                           48 hrs, no set                                   15    0.5%   Slag- Sodium                                                                              3 gpb                                                                             14 hrs set,                                            CaGH.sup.3                                                                           ment.sup.4                                                                          silicate  suitable                                                            100S      activator                                        15.8  0.5% NaGH                                                                            Port..sup.5                                                                         Dyn 531.sup.6                                                                       1.5 gpb                                                                           ineffective                                      15.8  0.5% NaGH                                                                            Port. STC.sup.7                                                                           1.5 gpb                                                                           ineffective                                      15.8  0.5% NaGH                                                                            Port. STC   3 gpb                                                                             slow activation,                                                              4 day                                            15.8  0.5% NaGH                                                                            Port. Sodium                                                                              3 gpb                                                                             16 hrs set,                                                         silicate  suitable                                                            120H      activator                                        15.8  0.5% CaGH                                                                            Port. Sodium                                                                              3 ppb                                                                             16 hrs. set,                                                        silicate  suitable                                                            100S      activator                                        __________________________________________________________________________     .sup.1 Sodium glucoheptonate                                                  .sup.2 The suspending agent for all slag slurries was 0.66 ppb xanthan        based on the mix water.                                                       .sup.3 Calcium glucoheptonate                                                 .sup.4 The suspending agent for all slagment slurries was 0.2 gpb             succinoglycan based on the mix water.                                         .sup.5 The suspending agent for all portland cement slurries was 3 ppb        bentonite clay based on the mix water.                                        .sup.6 "DYNAGUNIT 531", Sika GmBh, Germany                                    .sup.7 Sodium thiocyanate                                                

                                      TABLE 4                                     __________________________________________________________________________    RHEOLOGY OF STORABLE SLURRIES                                                    SLURRY       SUSPENDING                                                                            CEMENT                                                                              TIME                                                                              RHEOLOGY                                                                              COMMENTS                            NO.                                                                              DENSITY                                                                             RETARDER                                                                             AGENT.sup.1                                                                           TYPE  DAYS                                                                              PV/YP   21° C. (70°           __________________________________________________________________________                                              F.)                                 1  15    0.1%   0.66 ppb                                                                              Slag   0  150/9   small                                        NaGH.sup.2                                                                           xanthan.sup.3             change in                                                                     properties                                                        15  130/2                                       2  15.8  0.5%   3 ppb   Portland                                                                             0  39/20                                                CaG.sup.4                                                                            BC.sup.5                                                                                    14  42/30                                                                     21  49/32   small                                                                         change in                                                                     properties                          3  15.8  0.5% CaG                                                                             1.5 ppb Portland                                                                             0   52/8   very minor                                          PEO.sup.6                 changes in                                          1.5 ppb       33  54/11   properties                                          SSMA.sup.7                                                    __________________________________________________________________________     .sup.1 All concentration of suspending agent were based on the quantity o     mix water.                                                                    .sup.2 Sodium glucoheptonate                                                  .sup.3 Xanthan gum                                                            .sup.4 Calcium gluconate                                                      .sup.5 Bentonite clay                                                         .sup.6 Polyethylene oxide                                                     .sup.7 Sulfonated styrene maleic anhydride                               

                                      TABLE 5                                     __________________________________________________________________________    RHEOLOGY OF ACTIVATED SLURRIES                                                SLURRY                               RHEOLOGY                                 DENSITY SET            ACTIVATOR     PV/YP                                    (> DILUTED                                                                            RETARDER                                                                             SUSPENDING                                                                            Sodium  CEMENT                                                                              PRE-                                                                              POST-                                                                             COMMENTS                         DENSITY)                                                                              % BWOC AGENT.sup.1                                                                           Silicate.sup.2                                                                        TYPE  ACT ACT 21° C. (70°        __________________________________________________________________________                                                 F.)                              15      0.1%   .66 ppb 1.5 gpb 120H                                                                          Slag  147/8                                                                             150/5                                                                             little change in                         NaGH.sup.3                                                                           xanthan.sup.4                 properties                       15.8 > 15                                                                             0.5% CaG.sup.5                                                                       3 ppb BC.sup.6                                                                        3 gpb 100S                                                                            Port. 50/32                                                                             24/31                                                                             acceptable                                                                    after dilution                   15.8 > 15                                                                             0.5% CaG                                                                             1.5 ppb PEO.sup.7                                                                     2 gpb 100S                                                                            Port. 54/11                                                                             36/18                                                                             acceptable                                      1.5 ppb                       after dilution                                  SSMA.sup.8                                                     __________________________________________________________________________     .sup.1 The concentration of the suspending agent was based on the quantit     of mix water.                                                                 .sup.2 The concentration of activator was based on the quantity of slurry     .sup.3 Sodium Glucoheptonate                                                  .sup.4 Xanthan gum                                                            .sup.5 Calcium gluconate                                                      .sup.6 Bentonite clay                                                         .sup.7 Polyethylene oxide                                                     .sup.8 Sulfonated styrene maleic anhydride                               

                                      TABLE 6                                     __________________________________________________________________________    THICKENING TIMES.sup.1 OF ACTIVATED MIXES                                     SLURRY                                                                              RETARDER                                                                             Sodium CEMENT                                                                              SECOND T°C.                                  DENSITY                                                                             % BWOC Silicate.sup.2                                                                       TYPE  RETARDER                                                                             (°F.)                                                                       T.TIME MIN                                                                            COMMENT                         __________________________________________________________________________    15    0.1%   1.25 gpb                                                                             Slag.sup.4   71 (160)                                                                           360                                           NaGH.sup.3                                                                           100S                                                             15    0.1% NaGH                                                                            .25 gpb 100S                                                                         Slag         110  240                                                                      (230)                                        15    0.1% NaGH                                                                            .75 gpb 120H                                                                         Slag         110   93                                                                      (230)                                        15    0.1% NaGH                                                                            3 gpb 120H                                                                           Slag         71 (160)                                                                           200                                     15    0.1% NaGH                                                                            .75 gpb 120H                                                                         Slag         110  110                                                                      (230)                                        15.8 > 15                                                                           0.5% CaG.sup.5                                                                       1 gpb 100S                                                                           Port..sup.6  71 (160)                                                                           1037                                    15.8 > 15                                                                           0.5% CaG                                                                             1.5 gpb 100S                                                                         Port.        71 (160)                                                                           876                                     15.8 > 15                                                                           0.5% CaG                                                                             1.65 gpb 100S                                                                        Port.        71 (160)                                                                           406                                     15.8 > 15                                                                           0.5% CaG                                                                             1.8 gpb 100S                                                                         Port.        71 (160)                                                                           100                                     15.8 > 15                                                                           0.5% CaG                                                                             2 gpb 100S                                                                           Port.        71 (160)                                                                            56                                     15.8 > 15                                                                           0.5% CaG                                                                             2 gpb 100S                                                                           Port. 0.1 gpb                                                                              71 (160)                                                                           110                                                               R12-1.sup.7                                         15.8 > 15                                                                           0.5% CaG                                                                             2 gpb 100S                                                                           Port. 0.2 gpb                                                                              71 (160)                                                                           239                                                               R12-1                                               15.8 > 15                                                                           0.5% CaG                                                                             2.2 gpb 100S                                                                         Port. 0.2 gpb                                                                              71 (160)                                                                           125                                                               R12-1                                               15.8 > 12.5                                                                         0.5% CaG                                                                             2.2 gpb 100S                                                                         Port.        71 (160)                                                                            90                                     15.8 > 12.5                                                                         0.5% CaG                                                                             2.2 gpb 100S                                                                         Port.        49 (120)                                                                           225                                     15.8 > 15                                                                           0.5% CaG                                                                             3 gpb 100S                                                                           Port.        49 (120)                                                                           140     4 week                                                                        slurry                          15.8 > 15                                                                           0.5% CaG                                                                             3 gpb 100S                                                                           Port.        49 (120)                                                                           113                                     15.8 > 15                                                                           0.5% CaG                                                                             3 gpb 100S                                                                           Port.        49 (120)                                                                           101     1.4 ppb                                                                       SSMA.sup.8                      15.8 > 15                                                                           0.5% CaG                                                                             3 gpb 100S                                                                           Port.        49 (120)                                                                           116     0.35 gpb                                                                      NSAP.sup.9                      15.8 > 15                                                                           0.5% CaG                                                                             3 gpb 100S                                                                           Port.        49 (120)                                                                           190     0.35 gpb PA.sup.10              15.8 > 14.5                                                                         0.5% CaG                                                                             2.5 gpb 100S                                                                         Port..sup.11 71 (160)                                                                            77     1.5 ppb SSMA                    15 > 14.5                                                                           0.5% CaG                                                                             2.5 gpb 100S                                                                         Slag-        71 (160)                                                                            78     1.4 ppb SSMA                                        ment.sup.12                                               __________________________________________________________________________     .sup.1 Thickening time curves generally showed that 100 Bc were reached       quickly after thickening had begun. The activator and additional retarder     were mixed into dilution water, except for the runs with a density of 12.     lbm/gal where sea water was added first. Except where noted, tests were       done on freshly prepared mixes.                                               .sup.2 The concentration of sodium silicate is based on the quantity of       slurry.                                                                       .sup.3 Sodium glucoheptonate                                                  .sup.4 0.66 ppb (mix water) welan gum suspending agent for all slag           slurries                                                                      .sup.5 Calcium gluconate                                                      .sup.6 3 ppb (mix water) bentonite clay suspending agent for cement           slurries                                                                      .sup.7 Sodium lignosulfonate, 40% active, "BOREGARD                            .sup.8 Sulfonated styrene maleic anhydride                                   .sup.9 Naphthalene sulfonic acid polymer                                      .sup.10 Polyacrylate                                                          .sup.11 1.5 ppb (mixwater) PEO was used as a suspending agent and 1.5 ppb     SSMA was used as a dispersant.                                                .sup.12 The suspending agent for the slagment slurry was 0.2 gpb of           succinoglycan based on the amount of mixwater.                           

EXAMPLE 2

The following results were found when testing the compressive strengthusing the following formulation. An especially preferred storable slurrywas formed as described in Example 1 with portland cement, 0.5% CaG, 1.5ppb polyethylene oxide and 1.5 ppb sulfonated styrene maleic anhydride.The resulting slurry had a density of 15.8 lbm/gal.

The slurry was activated with 2.2 gpb 100 S sodium silicate and dilutedto a final density of 15 lbm/gal. At a curing temperature of 88° C.(190° F.), the following compressive strengths were measured.

    ______________________________________                                        TEST PERIOD (HRS)                                                                           COMPRESSIVE STRENGTH (PSI)                                      ______________________________________                                         8            1900                                                            24            3250                                                            48            3750                                                            ______________________________________                                    

As the above examples show, the slurries of the invention are stable andcan be stored for long periods of time while yielding excellentcompressive strengths. Because these stable slurries do not setimmediately, they can be made at one site and transferred to anothersite. For example, the slurries can be formulated at one location, suchas on land, with the density of the slurry measured and adjusted ifdesired. Next, the formulated slurry is transferred to a secondlocation, such as an offshore rig. At the second location thetransferred slurry may be immediately activated or stored until neededand subsequently activated. At the time of activation, additional mixwater and additives are added, while the slurry's density is adjusted toa desired density. The activated slurry is then pumped into the wellborefor the purpose of supporting the casing and isolating subterraneanformations.

An invention has been shown with several advantages. The ability tostore a liquid cement slurry eliminates onsite mixing problems,particularly the control of slurry density. Proportioning a liquidslurry with liquids, such as extra water or a weighting agent, is farsimpler than proportioning bulk solids with water.

Simpler equipment can be used with the storable slurries of theinvention. The slurries can be kept in nonpressurized tanks and loadedand unloaded with conventional fluid pumps. When cementing, the mixingunit need do no more than homogenize the fluid streams of the slurryplus additional mixwater and liquid additives en route to the downholepumps.

The ability to prepare and control the quality of a storable slurry atthe base is obviously advantageous. The slurry is mixed and its initialdensity measured and adjusted at the base rather than at the wellsite.The slurry need only be homogenized and activated during the cementingoperation. The stability of the slurry and longterm fluidity allow theslurry to be prepared, transferred and stored a considerable time beforeneeded for wellsite operations. Thus, the slurry may be prepared at acentral facility and stored in liquid form at the facility. From thereit is loaded aboard trucks or workboats and transferred to the remotewellsite. At the wellsite, it may be offloaded and stored or usedimmediately for cementing operations.

The slurry can be transferred with centrifugal pumps between storagetanks, transport tanks and downhole pumps much faster than dry cementcan be transferred pneumatically. Similarly, the time to offload cargoto an offshore location would be reduced. For land locations, the slurrycould be prepared at the rigsite while drilling is in progress or at acentral facility and truck to the wellsite, days before the cementingoperation and stored until needed.

The activated slurry can be easily modified to be used for a widevariety of cementing purposes desirable in oil and gas well cementingapplications. A few example of these properties include gas control,fluid loss control, turbulent flow rheology and high early strength.

While the invention is shown in only some of its forms, it is not thuslimited but is susceptible to various changes and modifications withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A method of cementing within a subterraneanformation for an oil or gas well, the method comprising the stepsof:formulating a storable, hydraulically-active, cementitious slurry bymixing together a hydraulically-active cementitious material of a typesuitable for cementing within subterranean formations for oil and gaswells, a set retarder, a suspending agent and water, wherein thestorable slurry's set characteristics upon activation are minimallychanged after storage; storing the storable slurry until required forcementing; activating the storable slurry by mixing together anactivator and the storable slurry; pumping the activated slurry into thesubterranean formation; allowing the activated slurry to set; whereinthe set retarder is present in an effective amount to allow the storageof the slurry with a minimal change of the slurry's set characteristicsupon activation and to allow the reversal of the retardation afteradding an effective amount of an activator to the slurry prior tocementing, the suspending agent maintains the slurry with minimalseparation of the cementitious material; and wherein an effective amountof activating agent is used to overactivate the slurry and an additionalset retarder is added to the slurry to achieve the desired setting time.2. The method of claim 1, wherein the set retarder is selected from thegroup consisting of:hydroxycarboxylic acids, glucoheptonates, ligninsulfonates, gluconates, phosphonates, and sugars.
 3. The method of claim1, wherein the suspending agent is selected from the group consistingof:welan gum, xanthan gum, carboxymethyl cellulose, polyanioniccellulose, carboxymethylhydroxyethyl cellulose, guar, starch,polyethylene oxide and succinoglycan.
 4. The method of claim 1, whereinthe suspending agent is bentonite or attapulgite.
 5. The method of claim1, wherein the slurry further contains a dispersant.
 6. The method ofclaim 5, wherein the dispersant is selected from the group consistingof:melamine sulfonic acid polymer, sodium polyacrylate, naphthalenesulfonic acid polymer, and sulfonated-styrene maleic anhydride polymer.7. The method of claim 1, wherein the activating agent is sodiumsilicate.
 8. A method of cementing within a subterranean formation foran oil or gas well, the method comprising the steps of:formulating astorable, hydraulically-active, cementitious slurry by mixing together ahydraulically-active cementitious material of a type suitable forcementing within subterranean formations for oil or gas wells, a setretarder, a suspending agent and water, wherein the storable slurry'sset characteristics minimally change upon activation after storage;storing the storable slurry until required for cementing; redispersingslurry particles during storage; measuring the density of the storableslurry; activating the storable slurry by mixing together an activator,additional water and the slurry; adjusting the density of the activatedslurry to a desired density; pumping the density adjusted, activatedslurry into the subterranean formation; allowing the activated slurry toset; wherein the set retarder is present in an effective amount to allowthe storage of the slurry with a minimal change of the slurry's setcharacteristics upon activation after storage and to allow the reversalof the retardation after adding an effective amount of an activator tothe slurry prior to cementing, the suspending agent maintain the slurrywith minimal separation of the cementitious material; and wherein aneffective amount of activating agent is used to overactive the slurryand an additional set retarder is added to the slurry to achieve thedesired setting time.
 9. The method of claim 8, wherein the set retarderis selected from the group consisting of:hydroxycarboxylic acids,glucoheptonates, lignin sulfonates, gluconates, phosphonates, andsugars.
 10. The method of claim 8, wherein the suspending agent isselected from the group consisting of:welan gum, xanthan gum,carboxymethyl cellulose, polyanionic cellulose,carboxymethylhydroxyethyl cellulose, guar, starch, polyethylene oxideand succinoglycan.
 11. The method of claim 8, wherein the suspendingagent is bentonite or attapulgite.
 12. The method of claim 8, whereinthe slurry further contains a dispersant.
 13. The method of claim 8,wherein the dispersant is selected from the group consisting of:melaminesulfonic acid polymer, sodium polyacrylate, naphthalene sulfonic acidpolymer, and sulfonated-styrene maleic anhydride polymer.
 14. The methodof claim 8, wherein the activating agent is sodium silicate.
 15. Amethod of cementing within a subterranean formation for an oil or gaswell, the method comprising the steps of:formulating a stable,hydraulically active, cementitious slurry at a first location by mixingtogether a hydraulically-active cementitious material of a type suitablefor cementing within subterranean formations for oil or gas wells, a setretarder, a suspending agent and water, wherein the slurry's setcharacteristics minimally change upon activation;. transferring theformulated slurry to a second location; activating the pumped stableslurry by mixing together an activator and the transferred stable slurryat the second location; immediately pumping the activated slurry intothe subterranean formation; allowing the activated slurry to set;wherein the set retarder is present in an effective amount to allow thestorage of the slurry with a minimal change of the slurry's setcharacteristics upon activation and to allow the reversal of theretardation after adding an effective amount of an activator to theslurry prior to cementing, the suspending agent maintains the slurrywith minimal separation of the cementitious material; and wherein aneffective amount of activating agent is used to overactivate the slurryand an additional set retarder is added to the slurry to achieve thedesired setting time.
 16. A method of cementing within a subterraneanformation for an oil or gas well, the method comprising the stepsof:formulating a stable, hydraulically-active, cementitious slurry at afirst location by mixing together a hydraulically-active cementitiousmaterial of a type suitable for cementing within subterranean formationsfor oil or gas wells, a set retarder, a suspending agent and water,wherein the slurry's set characteristics minimally change uponactivation; measuring the density of the stable slurry; after measuringthe density of the slurry, transferring the formulated slurry to asecond location; storing the transferred stable slurry at the secondlocation; activating the transferred stable slurry by mixing together anactivator, additional water and the slurry and adjusting the density ofthe activated slurry to a desired density; immediately pumping thedensity adjusted, activated slurry into the subterranean formation;allowing the activated slurry to set; wherein the set retarder ispresent in an effective amount to allow the storage of the slurry with aminimal change of the slurry's set characteristics upon activation andto allow the reversal of the retardation after adding an effectiveamount of an activator to the slurry prior to cementing, the suspendingagent maintains the slurry with minimal separation of the cementitiousmaterial; and wherein an effective amount of activating agent is used tooveractivate the slurry and an additional set retarder is added to theslurry to achieve the desired setting time.
 17. The method of claim 16,wherein the set retarder is selected from the group consistingof:hydroxycarboxylic acids, glucoheptonates, lignin sulfonates,gluconates, phosphonates, and sugars.
 18. The method of claim 16,wherein the suspending agent is selected from the group consistingof:welan gum, xanthan gum, carboxymethyl cellulose, polyanioniccellulose, carboxymethylhydroxyethyl cellulose, guar, starch,polyethylene oxide and succinoglycan.
 19. The method of claim 16,wherein the suspending agent is bentonite or attapulgite.
 20. The methodof claim 16, wherein the slurry further contains a dispersant.
 21. Themethod of claim 20, wherein the dispersant is selected from the groupconsisting of:melamine sulfonic acid polymer, sodium polyacrylate,naphthalene sulfonic acid polymer, and sulfonated-styrene maleicanhydride polymer.
 22. The method of claim 16, wherein the activatingagent is sodium silicate.